Replacing Calipers

[GDCobra]

The theory is doing the furthest longest run first is to remove the air from the longest first which might have the most air in. if you started at the shortest the brake pedal will always feel spongy with the air in the long run which feels both the back brakes.

That's a good point, so which line you start from doesn't affect the bleeding process but will remove more sponginess from the system soonest (which I guess may have an affect).
I typically use a pressure bleeder (similar to Ezi-bleed) which gives a constant flow so that should be less of an issue.

The large brake calipers upgrades on Jag brake I have seen on cobras, have bottom and top bleed nipples on the front calipiers. I find this very strange as the bottom one only lets air in so only do the top bleed in my experience. So why have a bottom one? Is it for left or right hand mounting of the caliper I guess. 

I have Wilwoods on mine which have nipples top and bottom, I guess they do that so they don't need to be right/left hand.
I do recall a thread on a forum (possibly this one) many years ago where someone was having trouble bleeding brakes, after many suggestions of how to fix it they put a photo' up clearly showing the nipples on the bottom as the calipers had been mounted on the wrong side!  The problem was solved soon after that.

[Deck]

Thanks for the replies.

I think it must have been something about pre-bleeding the master cylinder that was on my mind, that sounds familiar. This also sounds like I don't want to drain the system completely or I'll have a dry master cylinder...

I always found brake work to be messy, especially when changing the flexi's. I also have the problem that the reservoir is right under the wing, so it really is easiest to fill it with a big syringe/hose (also useful for emptying it!). Its a driparama! best done with cardboard protecting things. 

I have a little trigger vacuum pump that has worked pretty well but I will definitely try the grease on the thread as I have had this problem. I usually finish off with one of the boys on the pedal doing the push and hold routine to make sure.

Handbrake mechanisms are on top of these old units so no issues mixing them up.

I'll start by putting fresh fluid in the resevoir and doing the furthest one first, and doing one at a time.
Drip trays and tissue roll and new garage ready to go...

Thanks again
Declan

[JON1D]

The theory is doing the furthest longest run first is to remove the air from the longest first which might have the most air in. if you started at the shortest the brake pedal will always feel spongy with the air in the long run which feels both the back brakes.
I replaced a master cylinder some time ago and they suggested the best way was to bench bleed it first before install. It was the best thing I did as the brake bleeding was so easy working with no air in the master cylinder.
I then blocked off the front feed and bleed the rear. Again rock solid.

The large brake calipers upgrades on Jag brake I have seen on cobras, have bottom and top bleed nipples on the front calipiers. I find this very strange as the bottom one only lets air in so only do the top bleed in my experience. So why have a bottom one? Is it for left or right hand mounting of the caliper I guess.     

[GDCobra]

The method I have used is a Gunson easy bleed, you use a low pressure from a tyre to give you the required
pressure, be careful with this one otherwise brake fluid will be all over the place, you then go around your
braking circuit nipples as John mentions, furthest one first .
You need to physically check for any leaks with these systems .
Chris.

I also prefer the pressure rather than vacuum bleeding (I've always had issues with pulling air around the nipple threads with a vacuum pump - Could get around this if fitting new calipers by putting some grease on the threads) although this does require a reservoir which the EB has a cap for.

The important thing though is to make sure the calipers are all pointing the correct way so the nipples are the highest point so the air can escape otherwise you could push gallons of fluid through the system and still leave air in.

I've always been intrigued by the advice to start with the longest line first as I don't see what difference that makes or benefit it gives so if anyone can explain I'd be interested to hear.

[Chris]

Fully agree with Johns method, don't give yourself extra hassle/ mess .
The plant way of doing this was with a evac & fill setup, clamp goes on the top of the reservoir that pull a good
vacuum on the pre assembled dry braking/clutch circuits, then if no leaks are detected will then allow the system
to fill .
The method I have used is a Gunson easy bleed, you use a low pressure from a tyre to give you the required
pressure, be careful with this one otherwise brake fluid will be all over the place, you then go around your
braking circuit nipples as John mentions, furthest one first .
You need to physically check for any leaks with these systems .
Chris.

[JON1D]

No need to prefill the caliper you will just make a mess. Start at furthest brake and work you way around to shortest front corner.

I have found when doing your brakes on your own a suction pump vacuum system works great for pulling the fluid through and also pump your pedal at the same time .

Google "HAND VACUUM PUMP HELD BRAKE BLEEDER TESTER SET BLEED CAR MOTORBIKE BLEEDING KIT"

About £12 from Amazon or Ebay.

The first caliper will take 1/3 to 1/2 litre. I use the suction pump also to remove the old fluid first from the reservoir and top up with fresh DOT4.0. This saves you time and your not mixing old fluid in the reservoir.
 

[Deck]

Hi hi.

I've been away a while so good to see everyone going well! Had a quick search but my question is a bit basic!?

My cobra failed the MOT last week on rear brakes and handbrake (Sierra estate running gear). There has been a whittering coming from the back brakes for a while and as I had refubished them a few times over the years, I decided to just replace the calipers completely. Bigg Red were great and I got a really good deal on the calipers and HEL hoses for the whole car.

I have always had trouble bleeding the brakes on this car so I am wondering if its a good idea to pre-fill the calipers with fluid before connecting them up? And is there anything I need to do to the new calipers before I put them on? It's been a long time since I've had all 4 corners off!

New brakes...I won't know myself...

Thanks
Declan